The present invention relates to construction of railroad tracks, and particularly to the construction of railroad tracks embedded into the surface of a street or highway where automobile traffic will also travel, as at railway grade crossings and on streets where ligh-trail mass transport trains are operated.
Construction of railroad tracks along streets or across streets or highways has long presented the problem of how to present a minimum amount of unevenness to be encountered by motor vehicles operating on a pavement surface of such streets or highways. Additionally, if trains to be operated on such tracks are electrically powered, the track and its foundations are constructed to isolate the rails electrically.
If an open channel is left alongside a rail, entry of dirt and water can result in significant problems where railroad tracks run along a street and there is no ready path for drainage beneath the track. Various arrangements have been known in the past for providing a closed sealing structure around rails, particularly those rails which include a channel for receiving a flange of a car wheel, but such structural arrangements have previously been unnecessarily complex and undesirably costly.
It has been known in the past to install rubber filler bodies in place as seals along the rails of a track, and to place spacers alongside the seals after pavement has been constructed with the use of conventional masonry forms along the entire extent of the railway along or across streets and highways. Sealing material such as asphalt or the like has then been placed atop the spacers. Installation of such sealing material requires a considerable amount of labor, and such spacers and sealing material are somewhat lacking in ability to provide lateral support for the filler bodies. A considerable amount of labor is also required to remove such sealing material and spacers when it becomes necessary to remove the rubber filler bodies in order to repair the rails.
Austrian Patent No. 172157 discloses filler bodies associated with a railroad track rail set into a pavement, but shows no provision for fasteners attaching such a track rail to a supporting structure below pavement surface level.
Raymond U.S. Pat. No. 4,793,545 discloses sealing insert assemblies which extend along the length of the rails of an embedded track, but which appear likely to be costly to construct and yet unable to provide access to the rail support structure for repair.
Davis U.S. Pat. No. 5,181,657 discloses a grade crossing system including elastomeric pad units located along each side of the rails for supporting automobile traffic crossing railroad tracks. The disclosed structure, however, requires specially pre-cast panels which rest on the pads, making such structure undesirably expensive for use along a railway track embedded in a paved street.
Martin U.S. Pat. No. 4,899,933 discloses a railway crossing seal system which utilizes specially shaped pre-formed concrete planks on each side of a rail to retain rubber seal bodies. The structure taught by Martin thus appears likely to be excessively expensive for use over an extended distance along a railroad track embedded in a street.
Where tracks are embedded in pavement it is necessary to have a gutter to contain each rail, yet it must also be possible to gain access to the rail, its supporting structures, and fasteners attaching the rail to such supporting structures. Previously known protective caps intended to provide cavities around spaced-apart structures supporting the rails have been quite costly. Nevertheless, their use has not avoided the need for significant amounts of labor during the construction of an embedded railroad track, in order to provide support for pavement alongside each rail of a track, since a certain amount of space must be provided on each side of each rail to accommodate movements of the rails resulting from thermal expansion and contraction and from the loads imposed by the weight and movement of cars carried on the tracks.
Additionally, in order to avoid undesired unevenness of the surface of a street across or along which a railroad track runs, it is desirable that the pavement surface be approximately level with the height of the top of the rails of the track and that appropriate resilient filler structure be provided between the pavement and each rail to support motor vehicle traffic. Such filler structures, moreover, must not interfere with passage of railroad cars along the track.
What is desired, then, is an improved structure for railroad tracks embedded in a roadway, and a corresponding method for construction of such embedded railroad tracks and surrounding roadway pavement, which is easier and less costly than previously used methods and structures yet can provide long-lasting serviceability, while still giving needed access to the rails and supporting structures at lesser expense than has previously been possible.